The Irish man who uses the sun to make drinking water safer

Research Lives: Even Irish sunlight can be used to kill bacteria in water in glass or plastic bottles, says Prof Kevin McGuigan

Prof Kevin McGuigan is associate professor in the Department of Physiology and Medical Physics and director of the Solar Disinfection Group at the Royal College of Surgeons in Ireland

You use the sun to make water cleaner and safer. Can you explain? 

Hundreds of millions of people around the world don’t have access to safe drinking water. This causes diarrhoeal illness, which can be fatal, particularly for children under five. To carry out solar disinfection, you put water into a clear glass or plastic bottle and leave it in the sun for a few hours. This kills the bacteria and parasites that might otherwise make people sick.

How does solar disinfection work?

Ultraviolet rays from the sun damage the cell membranes of the bacteria and parasites, and also produce highly reactive chemical radicals inside the cell, which work like molecular chainsaws. The heat from the sun also helps to compromise the biochemical repair systems, so that’s a double whammy.

How did you start researching it?

About 20 years ago I was talking to Dr Joe Barnes, a retired tropical medicine lecturer at RCSI, and he wanted to look at how solar energy affects bugs in water. We started doing lab experiments and found that even the Irish sunlight was good at killing bacteria in water in glass or plastic bottles.

But does solar disinfection stop kids getting ill?

Our trials in Uganda, Kenya, South Africa, Zimbabwe and Cambodia show that solar disinfection of drinking water reduces diarrhoeal disease in kids under five by 25-50 per cent.

When I started I had a young child, so I always thought we would promote this on the basis of improved child health. But the knock-on effects are also really important – when kids are well, it means more kids in education, fewer need expensive medication and families can work more.

Did any of the trial results surprise you?

I was amazed to see that for the Maasai, at the end of the year-long trial the kids who had been drinking the solar-disinfected water were slightly taller than the control group.

This doesn’t sound like an office job 

I travel a lot to our field sites. Spending time with the people who would be using the solar disinfection is really important. The basic science isn’t everything – you have to understand the culture of the people you are working with.

Any good stories from your travels?

Lots. I remember doing experiments where I would take measurements of the water every hour and snooze under a tree in between. At one point I woke up to see two Maasai herdsmen drinking my experiment. I was about to ask them to move on when I noticed they were carrying enormous spears and machetes. So I figured I could just repeat the experiment the next day.

What’s next for the programme?

We have been supported by Irish Aid and by philanthropic funding to date, and we just got funding under the EU’s Horizon 2020 programme for a project called Waterspoutt. We will be looking at ways to use solar disinfection as an add-on to ceramic filters and rainwater-harvesting tanks, and also to run larger-volume solar disinfections.

What would you be if not a scientist? 

I can’t think of anything I would rather do than this research. I get to work in the most interesting and exciting places in the world, the outcome is rewarding and the experiences are life-changing.